The rich kelp forests surrounding the Commander Islands off the Alaskan Coast hosted the last of the Ice Age giants until 1768. Steller’s sea cows were manatees that diverged from tropical ancestors by evolving the ability to survive in frigid waters. This species was likely already in decline when discovered by Europeans in the middle of the 18th century. Sea cows formerly had a much larger range, occurring as far south as the Catalina Islands off the coast of California, but it seems likely indigenous fisherman were wiping them out before Europeans delivered the coup de grace to the final relict population just 37 years after discovering them. Some scientists think climate change caused the range reduction, but this seems unlikely because their favored habitat–kelp forests–remained widespread.
Killer whales hunt other whales. They must have hunted sea cows as well.
There are 20 ecotypes of killer whales. Scientists will eventually distinguish several species, but for now they are considered 1 species.
Sea cow range map. By the time Europeans discovered them, they were restricted to a final relict population located around islands off the Alaskan coast.
Artist’s rendition of a sea cow. They were big vegetarians that ate kelp all day. They did ram boats when hunted.
Steller’s sea cow was first described by George Steller, a German naturalist who sailed with a Russian exploration ship. (Their mission was to determine if Asia was connected to North America which it was during Ice Ages.) He had the chance to study sea cows when he was shipwrecked on Bering Island for 9 months. He published his description of sea cows along with the first scientific descriptions of northern fur seals, sea lions, and sea otters. He also found mammoth skeletons from a late population of them. He observed live sea cows and dissected dead ones. His work was difficult–arctic foxes, too naive to fear humans, swarmed his study area and stole his maps, books, and ink. He paid sailors with tobacco to help him dissect the beasts, and they complained. Nevertheless, his descriptions of sea cows are the only science-based observations we have. Sea cows were massive mammals 10 feet long and 20,000 pounds. They had tough skin and thick layers of blubber, and they traveled in small family groups. Gulls perched on them and fed on their parasites. The flesh was red and tasted like beef. Sea cow meat kept for a long time perhaps because the kelp they spent all day eating was high in nitrites, the same chemical used to preserve lunch meat. The blubber was reportedly as sweet as butter. Steller found 30 square feet of chewed up kelp in just 1 sea cow stomach, and dislodged, bitten off, kelp from sea cow feeding washed up on shore in great piles. Their stomachs were full of parasitic worms. When hunted by humans, sea cows would defend each other and ram boats.
I wonder how sea cows defended themselves from killer whales. Steller never saw any species preying on sea cows, but killer whales are known to attack blue whales–the largest animal to ever live. I’m sure the tough skin and thick blubber helped sea cows survive unsuccessful killer whale attacks. They likely placed themselves between killer whales and their more vulnerable calves, like whales, and they likely displayed communal defense and fought off killer whale attacks by ramming them. Their habitat may have been their best defense. They stayed hidden within kelp forests and were difficult to find for passing killer whale pods that didn’t know they were there.
There are 20 different ecotypes of killer whales, and they each vary in diet preference, genetics, appearance, and vocalization. Although there is only 1 official species of killer whale, that is likely to change soon. Scientists are on the verge of naming several new species after further study.
Reference:
Steller, G.; translated by W. Miller, J. Miller, and P. Royster
The Beasts of the Sea
Novi Commentaris Academiae Scientatum Imperiali Petropoitanae Tomii ad annum 1751
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